Measles virus-specific plasma cells are prominent in subacute sclerosing panencephalitis CSF

Abstract

Objective: To demonstrate the specificity of expanded CD138(+) plasma cell clones recovered from the CSF of a patient with subacute sclerosing panencephalitis (SSPE) for measles virus (MV).

Methods: IgG variable region sequences of single-antibody-secreting CD138(+) cells sorted from SSPE CSF were amplified by single-cell PCR and analyzed. Human IgG1 recombinant antibodies (rAbs) were produced from four expanded CD138(+) clones and assayed for immunoreactivity against MV proteins.

Results: Clonal expansion was a prominent feature of the SSPE plasma cell repertoire, and each of the four rAbs assayed was specific for either the MV fusion or the MV nucleocapsid protein.

Conclusions: Expanded plasma cell clones in the CSF of patients with subacute sclerosing panencephalitis produce disease-relevant antibodies. Recombinant antibodies derived from CSF B cells could provide a tool to identify target antigens in idiopathic inflammatory disorders.

Figure 1

Recombinant antibodies derived from expanded CD138⁺ clones in SSPE CSF immunostain MV–infected cells Purified recombinant IgG (10 μg/mL) from CD138⁺ clones 1 to 3 and subacute sclerosing panencephalitis (SSPE) CSF IgG stained measles virus (MV)-infected Vero cells, but not uninfected cells. Further immunostaining of Vero or HEK 293 cells transfected with cDNAs of individual MV proteins revealed reactivity of clone 1 rIgG with the MV fusion (MV-F) protein and reactivity of clones 2 and 3 rIgG with the MV nucleocapsid (MV-N) protein. CSF IgG from the patient with SSPE also stained both MV-N and MV-F transfected cells. Immunostaining was detected using a 1:500 dilution of goat anti-human IgG conjugated to alkaline phosphatase (Vector Laboratories, Burlingame, CA) with Vector new fuschin as substrate. Coverslips were counterstained with hematoxylin.

Figure 2

Immunoblot detection of MV–specific proteins with SSPE CSF-derived rAbs Measles virus (MV)-infected or -uninfected Vero cell lysates (15 μg/lane) were separated in a 10% sodium dodecyl sulfate polyacrylamide gel, transferred to nitrocellulose, and probed with each subacute sclerosing panencephalitis (SSPE) recombinant antibodies (rAb) (5 μg/mL) or with IgG eluted from SSPE brain. Antibody binding to MV proteins was detected using a 1:500 dilution of goat anti-human IgG conjugated to alkaline phosphatase. Under denaturing conditions, clones 1 and 2 rIgG did not recognize the MV-F or MV-N protein, whereas clone 3 rIgG did recognize a 60-kd MV protein. Although clone 6 rIgG did not immunostain MV-infected cells, it was weakly reactive with a 60-kd protein found only in the infected cell lysate, suggesting that clone 6 rIgG may also be directed against the MV-N protein. SSPE brain IgG also identified several MV-specific proteins.